1. Field of the Invention
The subject invention generally relates to a new and improved sensor for use as part of a safety system that is incorporated in a motor operated upwardly acting door. In particular, the safety system of the subject invention is used in upwardly acting doors that are in commercial and industrial applications.
Upwardly acting doors fall into three basic categories. First, there are sectional type upwardly acting doors that are generally constructed of various metals, woods and synthetic materials and comprise a plurality of individual sections which are fixed by mechanical hinge means to form a complete door of a size required for the given industrial or commercial application. The hinges extend along the longitudinal axis of each individual section and, at the end of each section, guide wheels are provided to allow the sections to follow along a pair of guide tracks to allow the door to move upwardly and downwardly to open and closed positions in a predetermined path. Usually, the door is in a vertical position when closed, and in a generally horizontal position when open.
Another form of an upwardly acting door is a one-piece door structure that is manufactured from various materials including wood, metal and synthetic materials. As the name implies, the entire door is produced to form a single panel, and numerous different designs exist to provide counterbalance and path guidance as the one-piece door is moved from the closed, generally vertical position, to the open, generally horizontal position. The one-piece door moves from the closed position to the horizontal open position by pivoting of the panel from the vertical plane and, at the same time, retracting it along the horizontal plane, thereby achieving the open position, at which point the door is generally horizontal.
Another common form of commercial or industrial upwardly acting door is generally referred to as a rolling steel door. Rolling steel doors are generally manufactured from various metals and consist of individual slats which are generally manufactured by roll forming to produce a desired shape. The slats are assembled by sliding one slat into another slat along a longitudinal axis to thereby form a curtain until the required door height is achieved, at which point a device is fixed to the end of the slats to prevent lateral movement thereof. The completed rolling steel door or curtain is then attached to a counterbalance assembly which applies the required forces to move the curtain in a vertical direction. As the rolling steel door or curtain is moved in a vertical direction, it is rolled about itself and stored around the counterbalance assembly to form a cylindrical shape. Usually, the counterbalance assembly has an outer cylindrical casing into which the rolled steel door or curtain is stored when the door is in the open position to allow access to the commercial or industrial building.
For each of the above-mentioned upwardly acting doors, it is well known to provide automated operation through the use of various mechanical means which are powered by either electric motors, hydraulic cylinders or pneumatic cylinders. All of the known automated systems employ an electrical or electronic control system to control the movement of the door as it travels between the open and closed positions.
In existing motor-operated door systems, usually a motor is electrically powered and turns a drum to either retract all of the panels into the storage container of the roll-up door when opening the door, or spool out the panels when the door is being actuated to its closed position. As part of the typical control circuit for an automatically opening door, it is usual to provide a sensing device which, upon encountering an obstruction in the door's path, automatically shuts off the electrical system for operating the door.
2. Description of the Related Art
One form of prior art safety device for an upwardly acting door is disclosed in U.S. Pat. No. 2,791,654 which issued on May 7, 1957 and is entitled “Combined Safe Edge and Sight Guard for Elevator Doors”. In U.S. Pat. No. 2,791,654 a combined safety edge and sight guard is provided for elevator doors using a microswitch which is closed when a cushioned edge is depressed by an interfering object.
Another prior art device is disclosed in U.S. Pat. No. 3,001,038 entitled “Overhead Closure Safety Halting System and Actuator Therefor” which issued on Sep. 19, 1961 and discloses an overhead closure safety halting system utilizing an actuating bar mounted on the leading edge of a garage door to close a switch when interference occurs.
In the prior art U.S. Pat. No. 4,115,952 entitled “Safety Door Edge” which issued on Sep. 26, 1978, there is disclosed a safety door edge that employs a flexible channel along the door edge containing a pair of contacts which come together when the channel is compressed.
U.S. Pat. No. 4,953,608 entitled “Safety Device, Particularly for Roll-Up Doors” which issued on Sep. 4, 1990 discloses a safety device particularly intended to be used in roll-up doors to cause reversal of the door closing movements in case an obstacle obstructs the path of movement of the door. The safety device of U.S. Pat. No. 4,953,608 includes a pair of photoelectric cells which are arranged at a certain distance from the closing edge of the door leaf in alignment with the door leaf on a support arm which is displaceable in the direction of closing of the door.
It is noted that none of the prior art discloses an upwardly moveable door safety system including a sensing device to sense when the overhead door is no longer level, whether it is in a vertical position or in the horizontal position. Furthermore, the prior art safety systems do not include a system having a sensing means which detects an obstacle in the door's path that causes the panels of the door to be misaligned horizontally, thereby causing the door to possibly jam and, if not corrected, causing structural damage to the door.
Accordingly, it is an object of the subject invention to overcome the shortcomings of the prior art safety systems and provide a safety system for an upwardly moving door including a sensing device that detects when a motor-operated door's panels are not horizontally aligned, whether the door is in the vertical or in the horizontal position.
It is a further object of the subject invention to provide a safety system including a sensing device that is simple and inexpensive to manufacture and is readily incorporated into the control system of an existing electrically operated automatic door.